comparing facial symmetry between photographs

In recent research, I received two photographs of unidentified women that were purported family members, and I wanted to explore a structured way of comparing them that could also be easily communicated as a two-dimensional still image for ease of publication/distribution. The following is the approach I took, and although I don’t know if this approach is valid, I thought the process and the results were interesting enough to warrant this description.

The one advantage I had was that the women in the two photographs were posed very similarly, and as I came to realize, the orientation of their heads is almost exactly identical. I wanted to see which facial features would align vertically and horizontally (or not) and so, I put them side-to-side and top-to-bottom in a visual matrix to compare both dimensions in one image. To properly align the photographs initially, I decided to use their eyes, as that doubled the initial reference points between the two photos, and further facilitated this visual matrix approach.

I began by cropping the faces of the subjects closer, and placed one on top of the other. I drew two vertical lines through the upper subject’s pupils, then resized the lower subject’s face until her pupil’s aligned.

Already, some useful comparisons can be made.

I then copied the lower subject to the right of the upper left subject to horizontally align the eyes.

I then copied the upper left subject to the lower right quadrant to fully enable the comparisons I wanted to explore. I then added parallel vertical and horizontal lines to see if other features aligned as well.

In this case, the similarities were very consistent.